Dewaxing wax-bearing oil



Sept. 15, 1936. F, X GOVERS 2,054,416

DEWAXING WAX BEARING OIL Filed March 19, 1954 Den/exea 0/7 Patented Sept. 15, A1936 DEWAXING: WAX-BEARING AOILY Francis X. Govers, Vincennes, Ind., assignor to Indian Refining Company, Lawrenceville, Ill., a corporation of Maine Application. March 19,

11 Claims.

This inventionv relates to the dewaxing of hydrocarbon oil and more particularly to an improved process oi removing parailin wax from wax-bearing petroleum` oil for the production of low pour testlubricating oil.

More specifically, my invention contemplates dissolving a wax-bearing oil in a suitable dewaxing solvent such as, for example,- mixtures of acetone and benzol or acetone, benzol and toluol. The resultant liquidi mixture is rapidly chilled to a temperature below 0f F. whereby the wax is precipitated and the chilled mixture filtered t'o separate the'precipitated Wax from the oil! and solvent in the form of a lter cake of slack wax. The lter cake is then washed at a low temperature with a quantity of the chilled dewaxing sol'- vent to remove therefrom any occluded oil. The solvent is nally separatedY from the dewaxed oil by a process ofV distillation. The lter cake of slack wax is similarly treated to free it from any retained solvent. The solvents arerecovered and returnedrto storage for reuse in the process.

'It is generally recognized that wax-bearing oils may contain either one or both of two typesy of paraffin waxeslow melting point waxes and high` meltingY point waxes. The removal of the latter from theoils vwith which theyare associated is usually a difcult undertaking with most oi the usual dewaxing solvents. For example, on diluting a wax-bearing oil containing high melt'- ingpointwaxes with naphtha.y and chilling the mixturathe wax separates out as minute crystals. The wax in this form tends toocclude the oil'insuch a manner that the mass can .be filtered only with great diiiiculty. the rates of ltration are so low as to be impracticable commercially andyieldsof. the dewaxed oilalso are W.

I' have discovered that by completely dissolving the wax-bearing oil ina suitable solvent, andthen chilling the. mixture rapidly to the desired de- Waxing temperature, the Wax content may be precipitatedinsuch-.aiform-that the chilled mixture may be; iiltered inan economical manner at rapidl rates. Moreover, the. resulting-wax cake is of such a character that it may eiectively be washed in situ with an additional portion of chilled solvent to remove theoil associated therewith. The ltrate thus'attained may be added to the main ltrate to produce a high total yield of Wax-free oil. Y

These facts are of considerable commercial significance inasmuch asthey enable substantial reductions tobe made in the cost of plants of a given-capacity, as comparedn with previous` prac- 1934, seriaiNo. 716.237

(ol. 19t- 18) tice' and, as indicated above, high yields oi finished oil may bersecured.

By the;term"suitable solvent`I mean a liquid which at temperatures of approximately 100 F. has substantially complete solvent action on a 5 Wax-bearing oil substantially free from constituents having a boiling point'equal to'or below that' off gas oil andat temperatures of 5 F. and vbelow has substantially-complete' solvent action on the-liquid hydrocarbons-'therein but sub- 10 stantially n'o solvent action on thesolid hydrocarbons therein and of sucha naturethat, Aupon cooling, a solution'of suchwaxbearing;oil to 0 F., 'and removing'the solid hydrocarbons so precipitated'and thesolvent liquid,` the resulting oil has 15 a pour test not'substantiall'y above 0 F;

As has already been pointedzout, If may employ armixtureof acetoneandbenzol or a mixture of acetone, benzolfand toluol'asva dewaxing solvent.

In the case: ofA then ormer,"I usually employ a 20 mixture consisting of in thetneighborhood of 35% of acetone and6`5% ofbenzol, however, the composition may vary depending on such factors as the type' of. oil, the type ofi` wax, as well as the quantities ofi waxv to be removed. The acetone, benzol, toluol mixture differs only in that commercial benz'o'lv whicl'r may contain varying proportions of toluol is substituted for the pure ben'- zol;

In additionto the above'described'solvent mix- 30 tures', I may. also employ mixtures such as acetone and toluol, sulfur dioxide and monochlor benzene, dichlor ethylene and sulfur dioxide.

The ratio of the suitable solventl to Wax-bearing oil used in operating in accordancewiththe present process is determined in part by the viscosity of" the oil undergoing. treatment and in part by the pourA point desired in the dewaxed oil.

Inr the case of low viscosity oils, a ratio o1Y three parts oi solvent tov one part of oil permits of the 40 most economical operation. In the case ofhigh viscosity oils', the ratio of solventl to oil is higher and'may be off the order of four or-iive. In all cases the choice of-` the'propersolvent-oil rat-io is also directly influenced by factors such' asA the 45 quantity of YWax present intheoil and the economies involved.

My inventionwill be more clearly understood fromvthe following description considered" in connection with the accompanying drawing where there is shown'afloW-diagram-in accordance with my invention. Y

In the operation. of-y the process a: charge of the proper amount of solvent is delivered into a gas-tight mixing; tank whichV isprovidedwith 56 may be conducted in any convetionalmanner.

-chilled dewaxing solvent.

YFor instance, the solutionmay be brought into heat interchange with brine cooled in a refrigerating plant or with directly expanded ammonia. The chilling isv conducted at a rapid rate which may be from 50 to 300 F. per hour.. The useof these high rates of chilling or #shock-chilling" as it is sometimes termed by those skilled in VtheV art isvof considerable importance. It hasbeen Yfound thatV the wax content is Vthereby precipitated in such a form that itcan be separated rapidly and effectively by a process of filtration. For filtering, a pressure lter is employed which is provided with means for washing the iItercake of separated wax.V Asfsoon as the filtration operation has proceeded to a point where'the filter cakeV of wax has built up to an optimum thickness, the filtration is stopped and anywuni'iltered Yoil is removed from the filter. The -filter cake is then Yblown with'flue gasto displace asi'much vof the solvent solution of oil remaining therein as possible, after which the wax cakeis thoroughly washed witha quantity of This serves to remove a large proportion of any of the remaining oil occluded in the wax cake. In this connection, it may be desirable to" chill the washing solvent to a somewhat lower temperature than that vof the'chilled suspension of crystalline wax in the solvent-oil solution to avoid solution of the slack Wax in the solvent. l Y Y The ltrate resulting from the iiltration operation is collected in a suitable manner. The dewaxingV solventV contained therein may be removed by' distillation to producethe finished waxfree oil. l Y

In a typical example, a wax distillate from a Mid-Continent crudehaving an A..P.` I. gravity of 25.0 and a' viscosity of Y61 seconds Saybolt Universal at 210 F. was treated in accordance with my process. This oil was mixed with three volumes of dewaxing solvent consisting of about 35%acetone and 65% of commercial 90% benzol, and the mixture was then brought to a tem- Y perature of about 105 F., at which temperature Y the mixture was thoroughlyV agitated to insure complete solution of the distillate in the solvent mixture.' The resulting solution was then rapidly chilled to a temperature of -10`F., at which temperature the wax was precipitated. The suspension ofprecipit'atedwax in solvents and oil `was then filtered ata temperature of about '10` F. whereby the wax Vwas separated. The 'separated wax while still in the'iilter was then V`subjected to washing with a quantity of the dewaxing' solventhaving a temperature of about l5 FQ whereby oil occluded in the wax was removedf The wash cntaininga small proportion' of oiiwasthen mixdfwitnthesolution of dewaxed Voil in solvent.

The solution ofdewaxedoil in solvent Was ithen 'subjected to'distillation whereby all of the solvent wasV removedfromthe wax-free' oil. The tests of Undewaxed Dewaxed oil Y oil Graviy, A. P. I 25.0 23.6 Viscosity Saybolt universal at F. in

seconds 557 712 Viscosity Saybolt universal at F. in

seconds 228 270 Viscosity Saybolt universal at 210 F. in

seconds 6l 66 Pour F -7 In the Yoperation of'fthe process it is desirable Y that the solvents be maintained substantially in an anhydrous condition. This is advantageously eiected by'washing the solvent mixture with a concentrated solutionV of sodium carbonate or by passing it through beds of salt, soda lime or other similar dehydrating agents which are chemically inert toward the solvent.V y Y Obviously many modiiications and variations of the invention, as hereinbefore set forth, may be made without departing `from the spirit and scope thereof,Y and therefore only such limitations should be imposed as are indicated inthe appended claims. u .Y

I claimr A l Y 1 A method of dewaxing a'wax-bearing oil comprising mainly constituents ofV cylinder stock viscosity which comprises mixing. the oil with a solvent dewaxing mixture' consistingY essentially of acetone and benzol, agitating the resulting mixture at a temperaturesuflicient to eiect complete solution of the wax and oil in the dewaxing solvent, rapidly chilling the resultant solution at a rate of from 50 to 300 F. per hour to a temperature of 0 F. or below whereby the wax is precipitated, separating the precipitated wax from the solution of dewaxed 'oil in solvent, washand then'sreparating the dewaxed oil from the solvents.

2.'A method of dewaxing a wax-bearing. oil comprising mainly constituents of cylinder stock viscosity which comprises mixing the oil with a dewaxing solvent consisting essentially' of about 35% acetone and 65% benzol, bringing the resulting mixture to an elevated temperature vsufiicient to eiiect complete solution of the wax andV oil in the dewaxing solvent, rapidly chilling the resultant solution to a temperature of 0 F. or below whereby the wax is precipitated, separating the precipitated Wax from the solution of dewaxed oil in solvents, washing the separated Wax with Aa portion of chilled dewaxing solvent mixture to remove remaining oil, and then separating the dewaxed oil fromthe solvent by distillation.

3. A'method of dewaxing a wax-bearing oil comprisingV mainly constituents of cylinder stock viscosity which comprises mixing the oil with a solventdewaxing mixture consisting essentially of acetone, benzol and toluol, bringing the resulting mixture to anelevated temperature suicient to effect'complete solution of the Wax and oil inv move occluded oil, and then separating the dewaxed oil from the solventby' distillation.

` 4. A method of dewaxing a wax-bearing oil comprising mainly constituents of cylinder stock viscosity: which comprises mixing the oil with a solvent dewaxing mixture consisting essentially of acetone and benzol topform a mixture, heating the' vmixture to a temperature above the solution temperature which characterizes the particular wax-bearing oil and the solvent dewaxing mixture to effect complete solution of the oil and wax in solvent, rapidly chilling the resultant solution to a temperature of below F. whereby the wax is precipitated, separating the precipitated wax from the solution of dewaxed oil in solvent by filtration in a lter, washing the wax in situ in the lter with a quantity of chilled dewaxing solvent to remove occluded oil, and then separating the dewaxed oil from the solvent by distillation.

5. A method of dewaxing a wax-bearing oil comprising mainly constituents of cylinder stock viscosity which comprises mixing the oil with a solvent liquid which at temperatures of approximately l00 F. has substantially complete solvent action on a wax-bearing oilsubstantiallyfree from constituents having a boiling point equal to or below that of gas oil and at temperatures of F. and below has substantially complete solvent action on the liquid hydrocarbons therein but substantially no solvent action on the solid hydrocarbons therein and of such a nature that upon cooling a solution of such wax-bearing oil in the solvent liquid to 0 F. and removing the solid hydrocarbons so precipitated and the solvent liquid, the resulting oil has a pour test of substantially not more than 0 F., bringing the resultant mixture to an elevated temperature sufficient to effect complete solution of the wax and oil in the dewaxing liquid, rapidly chilling the resultant solution at a rate of from 50 to 300 per hour to a temperature of 0 F. or below whereby the wax is precipitated, separating the precipitated wax from the solution of dewaxed oil in solvent, washing the separated wax with a portion of chilled dewaxing solvent mixture to remove occluded oil, and then separating the dewaxed oil from the solvent by distillation.

6. A method of dewaxing a wax-bearing oil comprising mainly constituents of cylinder stock viscosity which comprises mixing the oil with a solvent liquid which at temperatures of approximately 100 F. has substantially complete solvent action on a wax-bearing oil substantially free from constituents having a boiling point equal to or below that of gas oil and at temperatures of 5 F. and Vbelow has substantially complete solvent action on the liquid hydrocarbons therein but substantially no solvent action on the solid hydrocarbons therein and of such a nature that upon cooling a solution of such wax-bearing oil in the solvent liquid to 0 F. and removing the solid hydrocarbons so precipitated and the solvent liquid, the resulting oil has a pour test of substantially not more than 0 F., bringing the resultant mixture to an elevated temperature sufiicient to effect complete solution of the wax and oil in the dewaxing liquid, rapidly chilling the resultant solution at a rate of from 50 to 300 per hour to a temperature of 0 F. or below whereby the wax is precipitated, filtering the precipitated wax from the solution of dewaxed oil in solvent, and then separating the dewaxed oil from the solvent by distillation.

'7. A method of dewaxing a wax-bearing oil comprising mainly constituents of cylinder stock viscosity which comprises mixing the oil* with a solvent liquid which attemperatures of approximately 100 F. has substantially complete solvent action on a wax-bearing oil substantially free vfrom'constituents having a boiling 'point equal t0 orbelo'w that of gas oil and at temperatures of -5 F. and below hassubstantially'coinplete solvent action on the liquid hydrocarbons therein but substantially no solvent action on the solid hydrocarbons therein and of such a nature that upon cooling a solution of such wax-bearing oil in the solvent liquid to 0 F. and removing the solid hydrocarbons so precipitated and the solvent liquid, the resulting oil has a pour test of substantially not more than 0 F., bringing the resultant mixture to an elevated temperature sufiicient to effect complete solution of the wax and oil in the dewaxing liquid, rapidly chilling the resultant solution at a rate of from 50 to 300 per hour to a temperature of 0 F. or below whereby the wax is precipitated, separating the precipitated wax from the solution of dewaxed oil in solvent by ltration in a lter, washing the wax in situ in the filter with a quantity of chilled dewaxing solvent to remove occluded oil, and then separating the dewaxed oil from the solvent by distillation.

8. A method of dewaxing a wax-bearing oil comprising mainly constituents of cylinder stock viscosity which comprises mixing the oil with a dewaxing solvent having the essential solvent properties of a mixture of acetone and benzol, bringing the resultant mixture to an elevated temperature suiiicient to effect complete solution of the wax and oil in the dewaxing solvent, rapidly chilling the resultant solution at the rate from 50 to 300 F. per hour to a temperature of 0 F. or below whereby the wax is precipitated, separating the precipitated wax from the solution of dewaxed oil and solvent, washing the separated wax with a portion of chilled dewaxing solvent to remove occluded oil, and then separating the dewaxed oil from the solvent by distillation.

9. A method of dewaxing a wax-bearing oil comprising mainly constituents of cylinder stock viscosity which comprises mixing the oil with a solvent having the essential solvent properties of a mixture containing about 35% acetone and about 65% benzol, bringing the resultant mixture to an elevated temperature suiicient to eiTect complete solution of the wax and oil in the dewaxing solvent, rapidly chilling the resultant solution at the rate of from 50 to 300 F. per hour to a temperature of 0 F. or below whereby the wax is precipitated, separating the precipitated wax from the solution of dewaxed oil and solvent, washing the separated wax with a portion of chilled dewaxing solvent to remove occluded oil, and then separating the dewaxed oil from the solvent.

10. A method of dewaxing a wax-bearing oil comprising mainly constituents of cylinder stock viscosity which comprises mixing the oil with a dewaxing solvent having the essential solvent properties of a mixture of acetone and benzol, bringing the resultant mixture to an elevated temperature sufficient to eliect complete solution of the wax and oil in the dewaxing solvent, rapidly chilling the resultant solution at a rate of from 50 to 300 F. per hour to a temperature of 0 F. or below whereby the wax is precipitated, separating the precipitated wax from the solution of dewaxed oil in solvent, and then separating the dewaxed oil from the solvent.

A11. A method of rdevvaxing a wax-bearing oil comprising mainly constituents of cylinder stock viscosity'which comprises mixing the` oil with Va solvent having the essential solventproperties ofa mixture containing about 35% acetone and about 65% benzol, bringing the resultant mixture to an elevated temperature sufcient to eii'ect complete solution of the Wax and oil in the de- Vwax is precipitated, separating the precipitated wax from the solution of dewaxed oil in solvent. and then separating the dewaxed oil from lthe solvent by distillation.k Y g v j FRANCIS X. 'GOVERS 

